1. Field of the Invention
The present invention relates to a side support control device for use in a vehicle seat in which a motor is driven by means of a switching operation by an occupant of the seat to thereby control the operation of a side support so as to prevent the occupant from losing his or her sitting position.
2. The Prior Art
When a vehicle runs along curved roads, the occupant of the vehicle is subject to lateral forces that push the occupant to the side of the vehicle under the influence of centrifugal forces produced by driving around such curves. Due to this centrifugal force, the occupant may be forced to lose his or her sitting position, that is, the occupant may find it difficult to hold a predetermined sitting position and also the comfort of the occupant is greatly impaired. More particularly, if a driver is forced to lose his or her sitting position, then the driver's driving ability may be crippled thus endangering careful driving.
In view of the above, conventionally, there has been proposed and mounted to vehicle seats and particularly, the driver's seat, a side support control device which prevents the occupant from losing his or her sitting position by supporting the occupant properly.
For example, one of the conventional side support control devices includes a side support which is disposed in a seat back in such a manner that it surrounds the upper body of the occupant from both sides thereof. The side support is constructed such that it can press against the upper body of the occupant from both sides thereof to thereby restrict the occupant's upper body so as to be able to forcibly support the sitting position of the occupant. However, if the side support always presses against the upper body of the occupant from both sides thereof, then the freedom of the occupant's upper body is deprived thus impairing the sitting comfort of the occupant, which may make the occupant uncomfortable and/or tired. Thus, the side support is constructed such that it is normally situated in an open position in which the side support does not press against the occupant and it can be moved to a closed position (which is also referred to as a support position) only when it is necessary to support the sitting position of the occupant.
As the conventional side support control device, there is widely known a side support control device of a type that uses lateral accelerations (accelerations in the right and left directions) as parameters. The lateral accelerations can be detected directly by an acceleration sensor (for example, Japanese Utility Model Publication No. 60-97633), or they can be operated from the speeds of vehicles, the curvatures of curves and the like (for example, Japanese Patent Laid-open Publication (Tokkai) No. 61-67638). In this type of side support control device, if the lateral accelerations go beyond a reference value, then the side support is automatically moved to the support position thereof. Also, the parameters are not always limited to the acceleration. For example, in Japanese Utility Model Publication No. 60-97634, the vehicle speeds and the steering angles of a steering wheel are used as the parameters and, in Japanese Patent Laid-open Publication (Tokkai) No. 60-197436, the curvatures of curves and the vehicle speeds are employed as the parameters.
Also, there is known a so called "power" type of side support device which is arranged to move the side support directly by controlling the driving of a motor by means of a switching operation. In this system, as long as a switch is depressed, the motor is driven continuously, whereby arbitrary support or open positions can be manually set according to individual situations.
Now, as described before, in the first well known side support control device, the lateral accelerations, vehicle speeds, steering angles of the steering wheel and the like are used as the parameters, on assumption that the side support control device is used to control the side support when the vehicle is driven along the curves. For this reason, the side support control device is not able to control the side support properly when the vehicle is driven along bad roads or is caused to decelerate suddenly.
Also, the support position (or the closed position) that is most suitable for the occupant is not fixed but is varied according to the operating conditions of the vehicle. For example, when the vehicle moves along the curves, it is preferable to adjust the side support more narrowly (or harder) than in the normal support position thereof so as to ensure the stable position of the occupant. On the other hand, when stable driving conditions continue for a long time such as on expressways, it is preferable to set the side support more widely (loosely) than in the normal support position thereof, in order to prevent fatigue of the occupant.
However, in the above-mentioned well known side support control device employing the lateral accelerations and the like as the parameters, it is impossible to adjust the support position of the side support with ease according to the driving conditions.
Also, in this well known side support control device, after the side support is moved from the open position thereof to the support position thereof, for example, if the lateral acceleration which is being used as the parameter goes below the reference value and this condition continues for more than a given period of time the side support is to be returned to the open position thereof. For this reason, if the vehicle is repeatedly driven through curves in the mountains, for example, then the side support is frequently repeatedly opened and closed which is rather troublesome to the occupant. That is, such frequent repetition is not preferred from the viewpoints of careful driving and prevention of psychological fatigue.
On the other hand, in the side support control device of the power type, to move the side support during the driving of the vehicle, the switch must be depressed for a long period of time (up to about 8 seconds). For this reason, to control the side support during driving is not only troublesome but also provides an obstacle to safe driving, so that control of the side support during driving cannot be carried out easily.
Further, there are known side support control devices each of which is capable of controlling the support position of the side support properly according to individual situations by operating a switch. They are disclosed respectively in Japanese Patent Publication Nos. 62-101540 and 62-101541.
According to the above-mentioned type of side support control devices, it is possible to set a relax position which is looser than the support position selected by the occupant and a tight position tighter than the above-mentioned support position. And, by moving the side support from the support position to the relax position thereof or from the support position to the tight position thereof properly according to the situation, the occupant can be supported under a suitable pressure. Because of this, according to this type of side support control device, it is possible to adjust the support position of the side support easily according to the driving conditions of the vehicle.
The distances (that is, amounts of opening and closing) required for moving the side support from the support position (the initial position) thereof in the closing direction and in the opening direction in order to set the relax and tight position are different for the individual occupants and are not constant. Therefore, it is preferred that the amount of opening and closing can be easily adjusted quickly according to the tastes and physical condition of the occupants.
However, in the side support control devices respectively disclosed in Japanese Patent Publication Nos. 62-101540 and 62-101541, the amounts of opening and closing are previously set and thus, adjustment thereof according to the tastes and physical conditions of the occupants is difficult.